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battery



The textbook I am using states:
"The real battery, however, always has some
internal resistance r. As a result, the terminal
voltage is not equal to the emf."

I do not like the "as a result" phrase. We do
observe that the DOP between the terminals
becomes smaller when the load current goes
up. And then we invent a model, an ideal
batterry in series with a resistor. In reality
the difference between the emf and the DOP
may be due to something else than limited
conductivities. The change of resistivity
of wires (due to ohmic heating) is small and
the same is probably true for the electrolyte,
unless the number of free carriers drops
significantely.

The invented model is very useful but it is
not an explanation. A real explanation must
deal with some current-induced processes
taking place inside a baterry. What are they?
Ludwik Kowalski